


A Small Problem

by Vexatious



Series: Swapfell: Mutt in Heat [1]
Category: Undertale (Video Game)
Genre: Alternate Universe - Swapfell, Alternate Universe - Underfell, Alternate Universe - Underswap, Banter, Biting, Double Dicks, Double Penetration, Ecto-Genitalia (Undertale), Ecto-Penis (Undertale), Ecto-Vagina (Undertale), Explicit Language, Explicit Sexual Content, Foursome, M/M, Mating Cycles/In Heat, Multi, Multiple Penetration, Swapfell Papyrus - Freeform, Swapfell Sans, Threesome, Underfell Papyrus, Underswap Papyrus, Voyeurism
Language: English
Status: Completed
Published: 2017-11-25
Updated: 2017-11-25
Packaged: 2019-02-06 14:13:10
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,295
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/12819261
Author URL: https://archiveofourown.org/users/Vexatious/pseuds/Vexatious
Summary: Swapfell Papyrus is having a submissive heat cycle, and Swapfell Sans is ill-equipped to handle it….





	A Small Problem

**Author's Note:**

> Be sure to check out my [Tumblr](http://vex-bittys.tumblr.com)!

Blackberry knocked on the front door impatiently, then waited for someone to answer it with his arms crossed irritably over his armor-clad ribcage. The Underswap universe lacked the element of constant danger that defined the Fell universes, but old habits dust hard, especially when it comes to keeping up appearances.

The door creaked as it slowly opened about an inch. Stretch’s perpetually half-lidded eyes scanned the front porch to identify the visitor. The skull vanished without a word.

“It’s Blackberry,” the short skeleton heard his orange-hoodie clad acquaintance announce.

“WHAT DOES HE WANT?” a harsh, familiar voice asked. Edge? What was that smug bastard doing at the Swap brothers’ house? Actually, this situation worked in Blackberry’s favor. The two Papyruses were just the skeletons he needed!

Stretch hadn’t even closed the door properly when he’d gone back inside, so Blackberry simply let himself in, interrupting what he desperately hoped was inventive battle training and not some kind of strange foreplay.

Edge lounged on the sofa, his posture a clear indication of ownership of the space. His arms were draped across the couch’s spine, and his legs were casually parted to occupy the maximum amount of space. Stretch had seated himself, cross-legged, on the floor, a bowl of fish-shaped crackers in his lap. Blue magic encompassed one of the snacks, and the tiny, contrived food item went flying towards Edge’s face. A miniature red bone attack blocked it. Another cracker, another tiny bone deflection. Ridiculous! Edge actually looked relaxed though; maybe there was more to the snack attack than met the eye?

“I have a… small problem.” Two skulls turned to stare at him as if they’d already forgotten his presence. He scowled. He already hated having to swallow his pride and ask for help, and now these two doofuses were too busy playing with their food to pay proper attention! “Mutt is having a submissive heat and-”

“Aren’t all of Slim’s heats submissive?” asked Stretch, trying a tricky maneuver with one of his crunchy fish snacks.

“No. In fact… this is his first submissive heat since we’ve been together.” A tiny red bone materialized to batter the smiling cracker to the ground.

“YOU’RE THE DOM! WHY IS YOUR BROTHER HAVING DOMINANT HEATS?” The conversation derailed further, but Blackberry quickly explained his relationship with his brother. The defending magical bone flew forward and bounced itself off of Stretch’s nasal ridge.

“In Swapfell, we have specific roles. It pleases Mutt to top, to give me pleasure, so I allow him to do so. When he has heats, we continue with the same positions. In Swapfell, we value stability.”

“You take on Slim during dom heats?” Stretch asked, shocked. Slim’s insatiable sexual hunger was well-known throughout the multiverse, and many monsters underestimated Blackberry due to his small stature.

“Of course. He is my brother. I would do anything for him, anything to ensure his comfort and happiness, but now he’s having a very severe submissive heat and toys just aren’t working…”

“Make a dick.” Three goldfish crackers, shimmering with blue magic, surrounded Edge’s angular body.

“MAKE TWO DICKS.” Three glowing bone spears impaled the invading enemy force. Blackberry’s face flushed a pale blue-violet.

“As I mentioned, we each have our individual roles, and I’m not… ah… familiar with that type of magic.” Blackberry’s carefully constructed confident demeanor wavered a bit at the admission. “I… don’t think I could satisfy Mutt by myself. That’s why I came to ask for help.” Ugh. Had he been a typical callous, prideful denizen of the Swapfell universe, he would’ve simply let Mutt suffer his heat alone instead of degrading himself in such a manner, but Blackberry loved his brother more than himself.

“SOUNDS INTERESTING.” Edge commented.

“I’m in,” added Stretch.

Blackberry nodded, anxious to return to his brother. He’d left Mutt locked in his room with orders to dust anyone who entered without permission, but he didn’t trust any monster except himself when it came to Mutt, not even these other skeletons, not fully.

“Let’s go,” he snapped. Edge rose from the sofa, brushing away the crumbs of victory from his battle body and leather pants. Stretch rose to his feet too, flipping the bowl of leftover goldfish crackers onto the unsuspecting Edge. A rose blush colored Edge’s face as he flailed his arms to ward off the sudden influx of snacks.

“You’ve got a little something right there,” Stretch chuckled, pointing to a fishy shape tucked into a crease in Edge’s scarf. Edge growled and stomped towards the front door with Stretch’s laughter chasing behind him.

Weirdos.

* * *

Blackberry led the other two skeletons into his house and up the stairs. They exchanged weighted looks behind his back as he knocked softly, announcing himself before he unlocked the door. An intoxicating scent of citrus and spice permeated the hallway, exciting the magic of all three skeleton monsters.

Mutt faced away from his visitors on his knees, naked and tilted forward and thrusting three long bony digits in and out of his dribbling pussy. The lanky skeleton whimpered as Blackberry rushed to him. Edge and Stretch could see slick arousal glistening on Slim’s femurs and staining the bedsheets. Blackberry knelt beside his brother, rubbing his sweat-coated skull.

“Mutt, I told you to use the toys while I was gone!” Blackberry’s condescending sneer had faded away to be replaced by a gentle, concerned tone.

Mutt gave up his masturbating to tuck his massive frame against Blackberry’s much smaller body, ignoring the other two skeletons who regarded him hungrily but awaited permission to partake in his alluring heat cycle.

“It wasn’t enough,” Slim whined, the words muffled as he nuzzled his Lord’s neck.

“I brought Stretch and Edge to help you.” Blackberry waved them forward. Both of them displayed glowing bulges in their individual magic colors straining at their pants. Blackberry started to scoot away from his brother to make way for the other two tall skeletons, but Mutt clung to him, unfastening his chest armor with one hand.

“Please stay. Nothing turns me on more than the sound of your moans, m’Lord.” Even in the throes of a painful submissive heat, Mutt put his Lord first. Blackberry flushed at his brother’s words and the sentiment behind them.

“Both of us then?” he asked Mutt, who nodded as he began to lick Blackberry’s elegant neck. The small skeleton shivered, gesturing at the two waiting skeletons to begin. Mutt discarded his brother’s battle body, then allowed one hand to stroke the protrusions of his brother’s spine while the other hand, sticky with his own arousal, slipped down Blackberry’s shorts to probe at his Lord’s delicate folds. Blackberry moaned, drawing Mutt’s normally indifferent features into a loving smile.

The erotic aroma of Slim’s heat had Edge and Stretch breathing heavily, and Stretch fumbled with the button of his cargo shorts in his eagerness.

“DO YOU NEED HELP WITH THAT, ASHTRASH?” Edge purred against the side of Stretch’s skull, stepping in close behind his lazy double and sliding his hands sensually around Stretch’s hips to unbutton his pants. Stretch deliberately brushed the erection pushing against his backside as he turned in Edge’s arms and reached for the spikey asshole’s belt buckle.

“Only if you let me return the favor, Edgelord.” Leather and khaki hit the floor as the tall skeletons kicked off their pants and shoes and began palming each other’s cocks. As they rutted against each other, crimson precum mingled with orange, slicking and preparing their cocks for the upcoming task.

 

Blackberry’s shorts and boots had long since joined the growing clothing pile on his bedroom floor. Mutt suckled at his Lord’s neck, nipping each vertebrae harshly to draw breathy moans from his brother’s wide open mouth. Blackberry’s hands tangled in the blankets above his head as his brother gratified his body. Mutt’s dextrous phalanges found and massaged the spaces between each vertebrae in Blackberry’s spine, the places that Mutt knew his Lord carried all of the stress of their dangerous lives. Mutt’s other hand delved into the warm wetness of his brother’s tight pussy, gently stretching the summoned magic with each squelching thrust.

Edge lifted Stretch’s hoodie, tracing the other skeleton’s ribcage with his clawed fingertips. Stretch stroked his edgy counterpart’s spine in an innuendo-laden motion. Edge removed both of their shirts and tossed them aside.

“ARE YOU READY?” The imposing battle-scarred skeleton monster asked the two skeletons writhing and rubbing their bodies together on the bed.

“I think m’Lord is ready,” murmured Mutt into the curve of Blackberry’s shoulder as he removed his soaked fingers from his brother’s hungry slit. Blackberry gasped at the sudden feeling of emptiness and gasped again as a drop of his brother’s arousal fell onto his sensitive clit. Blackberry quickly wrapped his arms around his brother’s neck as Mutt lifted him off of the bed, holding tightly to his hips and angling them to display the puffy dripping lips of Blackberry’s soft little pussy to Edge and Stretch.

“Fuck,” Stretch groaned softly. That pussy reminded him of his own brother.

“I’LL TAKE SLIM,” Edge offered magnanimously, figuring that their gold-fanged copy would enjoy the squishy spikes that adorned his dark red length. He also noticed the wolfish way that Stretch stared at Blackberry.

Stretch agreed wordlessly, putting his hands on Blackberry’s hips right below Slim’s and lining himself up. Slim had done an excellent job prepping his brother. Edge stalked around until he was behind Slim, using one of his long legs to part Slim’s legs slightly and expose the twitching, dripping dark orange cunt that had been formed of lust and magic. How long had Mutt spent trying to stimulate himself with fingering and toys? How many times had he orgasmed already? How sensitive would he be? Edge was determined to find out.

 

Edge and Stretch both slipped into their chosen partners with little resistance, but Blackberry and Slim’s pussies were both tight, clenching and swallowing up Stretch and Edge’s cocks to the hilt despite their Papyrus-sized lengths and girths.

“Ahhh… Mutt,” Blackberry cried in pleasure as his eyelights rolled back from the feeling of being filled until his magic nearly burst. Mutt’s hands flew up from his Lord’s hips to his shoulder blades, phalanges digging into bone as he gripped Blackberry tightly and pressed their mouths together. Mutt couldn’t hold back his own cry as the spikes on Edge’s cock raked his sensitive walls. The gold fanged skeleton already felt close to orgasm, but nothing had satisfied him yet.

As the powerful thrusts from Edge and Stretch forced their bodies to press together, Mutt licked at Blackberry’s mouth, which opened willingly though Blackberry was dazed by the fierce and brutal pace Stretch set.

Edge, meanwhile, worked Slim’s pussy like a seasoned professional, putting the emphasis on power and speed as he pounded into Slim. One hand steadied the gold-fanged skeleton’s hips while the other hand played his clit like a virtuoso with his favorite instrument. Mutt’s tongue plunged harshly into his brother’s mouth as he came, sending a gush of hot fluids over the unrelenting hand and cock of the tall skeleton behind him. Stretch panted into Blackberry’s ear canal as he bucked his hips, pulling almost fully out before slamming back into the small skeleton. Mutt’s tongue wrapped around his brother’s, rubbing and suckling at him, swallowing down every mewl and moan that tried to escape his brother’s mouth.

 

Edge gyrated his hips wildly, changing his speed and angle to find new sensitive spots in Mutt’s hot cunt to abuse. The gentle rubs to Mutt’s engorged clit got rougher. Blackberry gulped at his brother’s tongue, wrestling it for control as bluish purple and dark orange saliva ran from the corners of their connected mouths. Mutt let a hand trail down his brother’s spine until he found the source of heat and dampness where Stretch’s cock connected him to Blackberry.

Mutt captured his Lord’s clit between thumb and forefinger and rolled it. Blackberry screamed for him, breaking their kiss and causing another hot gush of arousal to spill from Mutt’s cunt. The Swapfell skeleton brothers’ pussies clenched and trembled in unison as Blackberry followed his brother, his Mutt, to orgasm. Digging his fingers harshly into Blackberry’s hips, Stretch plunged fully into him once more, spilling torrents of pale orange seed from his cock and filling him to the brim until their mingled juices flowed out of the exhausted small skeleton’s gaping hole.

Edge held back, allowing the three other skeletons to achieve release first, but as his orgasm approached, he grabbed Mutt by the throat, tilting his head back and sinking his sharpened teeth into Mutt’s vertebrae as he shoved into him, jerking his hips as dark crimson cum spurted into Mutt’s pussy, letting his full load swell the gold-fanged skeleton’s conjured magic.

Edge and Stretch stepped back, breathing heavily with a light sheen of sweat on their bony brows. Mutt gently laid his Lord on his bed. Blackberry looked completely spent, and Mutt caressed his cheek, worried that the experience had been too much.

“Are you satisfied now, Mutt?” Blackberry rasped, voice rough from screaming. Mutt refused to meet his Lord’s eyelights. How could he tell his beloved brother that he still ached for more? Blackberry didn’t need Mutt’s words. He waved his arms officiously at Stretch and Edge.

“Please. He’s still experiencing his heat. Please continue.” Edge and Stretch nodded firmly. They’d known what they were getting into offering to help Mutt with a heat cycle.

“M’Lord,” Mutt protested quietly. Blackberry should be cleaned, cared for, taken to bed. Not left like this while he carried on enjoying himself.

“That’s an order Mutt. Besides, I want to watch them wreck you, and I want you to look at me and only me while you succumb to the pleasure.” Edge chuckled. He liked Blackberry’s style.

“Yes m’Lord.” Mutt stepped away from the bed and spread himself shamelessly for the other two skeleton’s, who quickly decided upon their positions.

Stretch, referencing his earlier conversation with Edge and Blackberry, had formed a second throbbing erection, and Edge pumped some extra magic into the spikes decorating his length. Moving to stand behind Slim one again, Edge kneaded the tender magic, bruised by the hard slaps of his hips from earlier. Even with the slick from their previous fucking still coating his dick, Edge knew it would be a tight fit. He began to lick the marrow-oozing bite mark he’d left on Slim’s neck while rubbing the tip of his hard cock against Slim’s tight, unused asshole.

Stretch stroked his double cocks lightly, making sure to lubricate them fully with the mixture of his and Blackberry’s cum. Leaning in close, he licked at the bite mark left by Edge as well, making sure to flick his light orange tongue against the dark red one. Edge hummed in pleasure, dragging Stretch into a kiss as he slowly pressed his twitching length into Mutt’s quivering asshole. Mutt let out a cry, and his knees wobbled slightly at the sudden, massive intrusion, but Stretch distracted him by burying both of his cocks into the stretched and gaping pussy that could barely take them both at once. Blackberry watched with interest as Mutt’s eyelights faded to nothingness briefly then returned as hearts. Maybe there was something to this highly masculine magic after all. Perhaps some training would be in order?

Edge and Stretch both had their sockets closed, absorbed in their sensual kiss over Mutt’s shoulder while they pushed forward, inch by inch into their respective holes. Stretch hilted first with a gasp that allowed Edge to fill his mouth with his writhing tongue. Edge’s sharp teeth nipped Stretch’s lower jaw as the scarred, edgy skeleton finally bottomed out inside of Mutt’s ass. The gripping tightness was almost too intense for the three skeletons, who paused for several long minutes while each of them adjusted.

Mutt whimpered as he felt the burning, painful need return. “F-fuck me.” he cried piteously, waggling his hips enticingly. The other two skeletons began to move, and pleasure exploded throughout Mutt’s entire body.Edge held his hips and Stretch clutched at his ribs as they simultaneously withdrew and sank into his yielding ecto-flesh. The tug and pull of his overfilled cunt and asshole had his tongue lolling and drool dripping onto his chest.

“GO HARDER, WEEDBAG!” snarled Edge, releasing Stretch’s mouth to take huge heaving breaths as he set a blistering pace.

Stretch couldn’t even form words. He could feel the spikes from Edge’s dick from inside of Slim. His own overstimulated members felt electrified with bliss, and if the moans and screams of the other two Papyruses were any indication, they were all feeling that abundant euphoria. How did Edge have so much energy to fuck? Edge’s powerful rhythm was hard to match, but Stretch bucked his hips forcefully, until Mutt screamed his brother’s name over and over, that single syllable fading away in nonsensical babbling as the pace suddenly began to stutter.

“FUCK… HE’S SO TIGHT…” The way Mutt’s asshole squeezed Edge’s cock eliminated any sort of staying power the edgy skeleton possessed. The pull and drag as he slid in and out was just too much.

“I’m… I’m… close…” Stretch muttered through gritted teeth. Mutt’s pulsating walls felt like they wanted to milk every drop of cum from both of his dicks, and he couldn’t deny them. Even Blackberry had begun to touch himself at the sight of the three tall skeletons, two of whom were fucking his brother into near-unconsciousness. It reminded him of the way Mutt fucked him during his dominant heats.

The raking barbs from Edge’s shaft against his dual dicks pushed Stretch over the edge first. He pinched and twisted Mutt’s clit as he came hard, hilted in the battered orange ecto-cunt. Mutt screeched his Lord’s name as his and Stretch’s magic swirled and filled him. Mutt’s orgasm caused a sudden tightening in his asshole that drove Edge to orgasm as well. Pale orange and deep crimson cum flooded Mutt’s body in heavy sticky strands. It spilled out thickly once there was no more space inside the ravaged pussy and asshole to hold it.

Edge and Stretch didn’t pull out right away. Mutt had collapsed against Stretch’s chest and only Edge’s strength held the other two Papyruses upright. They needed a moment for their magic to calm down. Blackberry got to his feet and lifted his much taller brother into his arms as Stretch and Edge dismissed their magic. Mutt was a mess, such a mess that normally Blackberry would’ve bathed him before allowing him into his immaculately clean bed. However, Mutt slept too soundly and peacefully to disturb just as Blackberry had hoped.

Placing his brother in a comfortable position and covering him with a blanket, Blackberry turned to his knights in now-less-than-shiny armor. “Will you stay? He might need more attention when he wakes.” Blackberry absently petted Mutt’s skull, and the larger Swapfell skeleton made a happy murmur at the affectionate gesture without opening his sockets or awakening.

“FINE,” snapped Edge, snatching his clothes off of the floor. “I CALL FIRST SHOWER THOUGH.”

Stretch made an indistinct noise of agreement, picking up his own clothing. He and Edge exited the room into the hallway before Stretch properly spoke again.

“You can call first shower all you want, Edgelord. I won our sparring match earlier. Shower or not, I top tonight,” Stretch gave his angular accomplice a sly smirk.

“There were extenuating circumstances,” hissed Edge, opening the bathroom door.

“Aww, don’t be like that, Edge. Besides, you’re going to be a  _really_ sore loser by the time I’m done with you.”

The bathroom door slammed in Stretch’s face, but not before he saw the bright red blush glowing on Edge’s pointy cheekbones.


End file.
